Automatic volume-control system



Sept. 30, 1930. M. E. STRIEBY AUTOMATIC VOLUME CONTROL SYSTEM Filed May 21, 1927 I N V EN TOR. ME ma ATTORNEY I control systems and 1 lation is a energy transmitted over or t UNITED STATES PATENT OFFICE,

MAURICE E. STBIEBY, OF MILLIBUBN,

NEw JERSEY, ABSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YOR AUTOMATIC VOLUME CONTROL SYSTEM Application med Kay 21,

' This invention relates to automatic volume particularly to means the volume of rough atransmitting medium so that it will atall times for automatically controllin have a predetermined relation to the volume of the ener y at the source, thereof, which reunction of the volurfie of the signal to be transmitte In the transmission of over or through a transmittin electrical energy medium such as a telephone circuit, it may e desirable to change the volume of energy to be transmitted to bring it within the limits of transmission of the telephone circuit. If the volume transmitted is excessively high, crosstalk will be produced in adjacent circuits. On the other hand, if the volume falls below the level of noise on the telephone circuit, distortion of the signal will result. Various ways have been proposed heretofore to vary the volume of energy that is impressed by some source upon a telephone transmission circuit to keep the volume as transmitted Within the limits described above. Those methods employingsome form of manual control have been expensive andvfrequently not satisfactory because of'the inherent delay. In the automatic systems of the prior art distortion has been produced by the fact that the operation is instantaneous and con tinuous.

My invention resides in means for auto-- matically controlling the Volume of energy to be transmitted over or through a transmitting medium so that the volume as transmitted will at all times bear a predetermined relation to the volume of energy from the source connected with the transmittingmedium.

The other objects of this invention will be apparent from the. following description when read in connection with the attached drawing showing schematically a form of the invention in which the volume control is effected by the operation of devices controlling the efi'ective connection of shunt circuits across the input of the connecting amplifier.

In the drawing, 1 represents a source of energy which is connected with an input cir- 1927. Serial No- 193,366.

ample, a transmltter adapted to translate sound into electrical energy, the latter vary ing with changes in volume of the sound im pressed upon the transmitter. The inputcircuit is conected with the rimary winding 2 of the transformer T The secondary winding 3 is connected with the grid of the amplifier 4, the plate circuit of which is connected by the transformer T with a line circuit L or to a rece'ivin device which may have predetermined limits as to the volume that may be efficiently handled thereby. circuit of the amplifier 4 is shunted by a plurality of paths, each having therein a gaseous discharge device, such as a neon tube, and a resistance one purpose of which is to extinguish the discharge of the tube after operated and the applied voltage has fallen again to lower limits. A source ofpotential 39 is adapted to apply a biasing voltage to the said tubes so that each will operate at a voltage from the line L differing from that of the others. Thus, the tube 44, which has the maximum biasing voltage applied thereto, would be biased by smallest increase above normal in the volume of energy being transmitted over the line L. The operation of this tube places a relatively low impedance path across the secondary 3 of the transformer T and thus reduces the voltage applied to the grid of the am lifier 4 The gain of the amplifier is accor ingly reduced and, in consequence, the volume of energy transmitted over the line L is less than it would have been had not the tube 44 broken down. With successive increases in Volume upon the line L, the remaining neon tubes will successively operate as the applied voltage reaches their operating values, and other shunt paths of relatively lower impedance will be ary of the transformer, thus further decreasing the gain of the amplifier 4. As the volume upon the line L tended to diminish after reaching a certain abnormally high value,

the voltage across the tubes would gradually The input it has 39 to break down at the tubes would be extin drop in value and the discharge through the ished, the operation beingfacilitated by t e resistances 45 to 49, inclusive, connected in series with the said tubes. In this way, the shunt paths would be efiectively opened one after another and the amplifier gain correspondingly increased.

The arrangement shown in the drawing is characterized by instantaneous action of the volume control devices so that delay circuits are not required. The system is further characterized by simplicity and relatively low cost.

While the invention has been described in connection with a transmission line having predetermined limits as to the volume it is capable of efiiciently handling, it may be employed in other ways. Thus, for example, it may be used in the making of phonograph records, in which it is desirable to reduce the volume so that it will be within the limits that the recording means is capable of handling. Furthermore, the invention may be employed as an expander as well as a compressor.

The form in which the invention is disclosed is purely schematic and it is, of course, obvious that the invention may be embodied in other forms without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In an automatic volume control system, the combination with a source of energy, the volume of which is subject to variations, a transmitting medium, an amplifier having its output circuit connected with the said medium, connecting means to apply the voltage of the said source to the said transmitting medium, a plurality of gas discharge de vices, each in series with a source of biasing voltage, the magnitude of which will cause each of said devices to break down at a voltage from the said source different from the breakdown voltages of the others, the said devices being bridged across the input of the said amplifien whereby the gain of the said amplifier may be varied.

2. In an automatic volume control system, the combinatiolrwith a source of energy, the volume of which is subject to variations, a transmitting medium, an amplifier havingits output, circuit connected with the said medium, connecting means to apply the voltage of the said source to the said transmitting medium, a voltage control system connected between the said amplifier and the said connecting means comprising a plurality of gas discharge devices, each in series with one of a plurality of resistances, each differing in magnitude from the others, and each of said devices being potentially biased to a degree differing from that of the others whereby thegain of'the said amplifier varies with changes in the volume of the said source. 3. In an automatic volume control system,

the combination with a source of energy, the volume of which varies with time, of a transmitting medium, and means to vary the volume applied by the said sourceto the said transmitting medium, the said means including a transformer connecting the said source and the said amplifier and a plurality of shunt pathsnormally of relatively high impedanceacross the input of the said amplifier, each path including a neon tube biased by a direct potential, the said potentials differing for'the various tubes whereby each operates at a different potential from said source to reduce the impedance of the shunt paths.

4. In an automatic volume control system, the combination with a source of energy, the volume of which varies with time, of a transmitting medium, having well defined volume limits, and means to vary the volume applied by the said source to the said transmitting medium, the said means including a transformer connecting the said source and the said amplifier and a plurality of shunt paths normally of relatively high impedance across the input of the said amplifier, each path including, a neon tube biased by a direct potential, the said potentials diflering for the various tubes, whereby each operates at a different potential from the said source to reduce the impedance of the paths, and a resistance connected in each of said shunt paths, the magnitudes of the various resistances differing from each other.

In testimony whereof, I have signed my name to this specification'this 20th day of May, 1927.

MAURICE E. STRIEBY. 

